Planting spacing and NK fertilizing on physiological indexes and fruit production of papaya under semiarid climate

ABSTRACT The nutritional requirements of papaya (Carica papaya L.) increase continuously throughout the crop cycle, especially for potassium and nitrogen, which are the most required nutrients and act on plant vital functions such as photosynthetic activity, respiration, transpiration and stomatal regulation. An experiment was conducted from November 2010 to December 2012 to evaluate physiological indexes and fruit production of papaya cv. Caliman-01 as a function of planting spacing and NK fertilizing. The experimental design consisted of randomized blocks, with treatments distributed in a factorial arrangement (2 × 4 × 4), using 2 planting spacing [simple rows (3.8 × 2.0 m) and double rows (3.8 × 2.0 × 1.8 m)], 4 nitrogen doses (320, 400, 480 and 560 g of N per plant-1) and 4 potassium doses (380, 475, 570 and 665 g of K2O per plant-1) with 4 replications of 3 plants each. The following variables were evaluated: leaf area index (LAI), leaf chlorophyll index (a, b and total index), intercepted photosynthetically active radiation (Int.PAR, in µmol∙m-2∙s-1), efficiency use of photosynthetically active radiation (Ef.PAR) and fruit yield. The fruit production and physiological characteristics of papaya cv. Caliman-01 depend on planting spacing. Under the soil, climate and plant conditions of this study, 665 g of K2O and 320 g of N per plant under double spacing could be recommended for the production of papaya cv. Caliman-01